1. Field of the Invention
The present invention relates to an image forming apparatus and, more specifically, to an image forming apparatus such as a digital copying machine so structured as to develop an image once on a page memory at the time of image data output.
2. Description of the Related Art
Recently, in a digital copying machine with a memory, editing operation of screening a read image to produce a halftone image and combining with another read image has come to be performed.
For example, U.S. Pat. No. 5,146,554 discloses a technique of shading data developed by a character generator. Japanese Patent Laying-Open No. 4-26273 discloses a technique enabling registration of screen pattern read by a scanner in an apparatus performing screening on an original.
Further, Japanese Patent Laying-Open No. 4-10960 discloses a technique of screening printed characters only, in a printer.
However, when a plurality of images are to be screened and combined to be output, it is necessary to perform screening operation on images developed in separate areas, and to superpose respective screened images. More specifically, a first image is developed in a page memory for output and screening, the second and the following images are developed in different areas for screening, and the screened images are superposed on the page memory for output. As a result, extra memory corresponding to the area for screening is required, increasing cost.
In addition, when a plurality of images are to be screened with different densities to be combined, it is necessary to screen the images developed on separate areas, and to superpose the screened images thereafter. As a result, in this case also, extra memory corresponding to the area for screening is required, increasing cost.
Therefore, an object of the present invention is to provide an image forming apparatus capable of processing at a low cost when an image is to be formed by screening and combining a plurality of images.
Another object of the present invention is, in an image forming apparatus, to form an image by screening and combining a plurality of images with small memory capacity.
A further object of the present invention is to provide an image forming apparatus capable of processing with small memory capacity when an image is to be formed by screening and combining a plurality of images.
The above described objects are attained by the image processing apparatus including an image reader for reading images and a printer for printing images read by the image reader, characterized by a page memory for developing, with screening, a plurality of images read by the image reader, and a controller for developing data of the plurality of images on the page memory such that screen patterns of the data of the plurality of images are superposed on the page memory.
When the plurality of images read by the image reader are combined and output, the screened images are developed on the page memory such that the screen patterns of the images are superposed. Therefore, it becomes possible to develop images on the same area in the page memory, and it becomes unnecessary to develop screened images on separate areas when the screened images are to be superposed. Therefore, the page memory can be reduced by that amount.
As a result, an image forming apparatus capable of processing at a low cost when an image is to be formed by screening and combining a plurality of images is obtained.
According to another aspect, the image forming apparatus includes an image reader for reading images and a printer for printing the images read by the image reader. The image forming apparatus includes a page memory for developing, with screening of mutually different densities, data of the plurality of images read by the image reader, and a controller for developing data of the plurality of images on the page memory such that screen pattern of lower density on the data of the plurality of images is covered by a screen pattern with higher density.
In a structure in which images read by the image reader are developed on a page memory and output, when a plurality of images with different densities are to be screened, combined and output, the images are displayed on a page memory such that screen patterns of respective screened images are superposed with each other and that a screen pattern having lower density is covered by a screen pattern having higher density. Accordingly, it becomes possible to develop images on the same area of a page memory, it becomes unnecessary to develop screened images on separate areas when the screened images are to be superposed and, by that amount, the page memory can be reduced.
As a result, an image forming apparatus capable of screening a plurality of images with smaller memory capacity is provided.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.